[be] Flag and test for unexpected exceptions during compilations

compiler/packages/babel-plugin-react-forget/src/Entrypoint/Pipeline.ts

@@ -361,6 +361,15 @@ function* runWithEnvironment(
   const ast = codegenReactiveFunction(reactiveFunction).unwrap();
   yield log({ kind: "ast", name: "Codegen", value: ast });
 
+  /**
+   * This flag should be only set for unit / fixture tests to check
+   * that Forget correctly handles unexpected errors (e.g. exceptions
+   * thrown by babel functions or other unexpected exceptions).
+   */
+  if (env.config.throwUnknownException__testonly) {
+    throw new Error("unexpected error");
+  }
+
   return ast;
 }
 

compiler/packages/babel-plugin-react-forget/src/HIR/Environment.ts

@@ -281,6 +281,12 @@ const EnvironmentConfigSchema = z.object({
    * Intended for use in demo purposes (incl playground)
    */
   enableMemoizationComments: z.boolean().default(false),
+
+  /**
+   * [TESTING ONLY] Throw an unknown exception during compilation to
+   * simulate unexpected exceptions e.g. errors from babel functions.
+   */
+  throwUnknownException__testonly: z.boolean().default(false),
 });
 
 export type EnvironmentConfig = z.infer<typeof EnvironmentConfigSchema>;

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/error.handle-unexpected-exception-pipeline.expect.md

@@ -0,0 +1,23 @@
+
+## Input
+
+```javascript
+// @throwUnknownException__testonly:true
+
+function Component() {}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [],
+};
+
+```
+
+
+## Error
+
+```
+unexpected error
+```
+          
+      

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/error.handle-unexpected-exception-pipeline.ts

@@ -0,0 +1,8 @@
+// @throwUnknownException__testonly:true
+
+function Component() {}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [],
+};